Many years ago, I started to buy small gold charms specifically with Jewish symbols for my mother who added them to a necklace, much like gold charm bracelets circa 50 years ago. Among them were tiny mezuzas, menorahs, a chai, luchot-habrit, magen davids, a hamsa, and one that said "mazal" in Hebrew. It was special for me to find and gift her with a new-found charm to add to her chain. Some years ago she stop wearing it. After she passed away, I began to wear it myself, until a friend of my mother's told me that one rabbi told her that wearing these charms (or maybe it was the "mazal" charm specifically) was avodah zarah. Being the good and Torah true person she was, she took off that necklace that she normally wore all the time and did not wear it again.

Could someone please clarify for me? Are charms like this considered avodah zarah? If so, what is the source for this?